<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<script>
  class Class1{}
  let c1 = new Class1();
  let map = new Map();
  // let map = new WeakMap();
  map.set(c1, 1);
  c1 = null;

  ({a:1,b:2})
</script>
</body>
</html>
